EAST RUTHERFORD, N.J. - The offense was emblematic of the chilly weather on the 42-degree afternoon.
Borland made his second game-sealing turnover in as many weeks, when he snagged a fourth-down pass deflected by fellow rookie Dontae Johnson at the goal line with less than five-minutes to play up by six.
New York lost its fifth straight while the 49ers got their sixth win of the year. San Francisco enters a stretch of four of six played on its home field as they push the for their fourth straight playoff berth.
The Seahawks lost on the road to the Chiefs, 24-20 Sunday, putting the 49ers in a second-place tie in the NFC West.
"That was a spectacular performance by our defense today," head coach Jim Harbaugh said. "So many guys, so many guys stepped up and played great. Rising to the moment, competing like the dickens."
Once again, the 49ers offense was plagued by issues in the red zone. Their only touchdown of the day - a Michael Crabtree 48-yard catch on their first possession in the second half - came from well outside the 20. They finished 0-4 on red zone attempts.
Kicker Phil Dawson was the 49ers' leading scorer, kicking three first-half field goals. San Francisco botched his only try in the second half thanks to a low snap from Kyle Nelson, who made his first noticeable error of the season in his first year long snapping for the 49ers.
On San Francisco's first drive of the day, Frank Gore fumbled on a misdirection run at the 19 and the Giants recovered the ball after it bounced out to the 31-yard line, where it was recovered by Corner Zack Bowman.
Five no-huddle plays later, the Giants scored the game's first points on tight end Larry Donnell's 19-yard TD grab up the seam over linebacker Michael Wilhoite.
A defense that came into the day ranked as the league's No. 2 unit had its most opportunistic showing of the season, allowing just 6-15 third-down conversions to the Giants' offense and forcing a season-high five turnovers.
Manning passed 45 times, often getting pressured by defenders, and completed just 22 throws for 280 yards. He came into Sunday with six interceptions on the season and finished with 11.
"It was obviously the accuracy issue," Giants coach Tom Coughlin said. "He had great pressure and I don't think anybody's going to argue with that one."
Three passes were fades on the team's final red-zone try, when it couldn't punch it in from four yards out late in the fourth quarter following Odell Beckham Jr.'s acrobatic, juggling 37-yard catch along the right side line.
It was the most pivotal moment of the game for New York, who would have taken the 17-16 lead with a touchdown and extra point after San Francisco's offense had stalled for the majority of the second half.
The Giants tried fades to three different receivers. The first went to Beckham on the right side. Ruben Randle (7 catches, 112 yards) couldn't haul one in over Chris Culliver on the left. Then safety Eric Reid prevented the 6'6" Donnell from coming down with control of the ball on third down.
On fourth down, Manning felt pressure and didn't have anyone open. He spotted wideout Preston Parker to his immediate left along the goal line. But Johnson was there and tipped the pass to Borland for his second interception of the day.
"In hindsight, we should've run the ball," Coughlin said.
The 49ers got back outside linebacker Aldon Smith from his nine-game suspension, who missed the first quarter before playing regularly once he was inserted into the game. He didn't register a sack, although he came close on the Giants' final drive in the fourth quarter, but made his presence felt and contributed to Manning's struggles.
"It was exciting. Like you’re first day of school," Smith said.
Smith's use came to the detriment of Ahmad Brooks, who did not return to the game after he was replaced by Smith in the first quarter. The 49ers said Brooks did not suffer and injury. Harbaugh was ambiguous with the reasoning Brooks was sidelined in favor of Smith and rookie Aaron Lynch, who notched his third sack in his last four games.
"We have something we are working through," Harbaugh said.
[Related: Brooks benched in Smith’s return]
Reid, Culliver and Wilhoite also notched interceptions. But the 49ers only came away with three points off Giants' turnovers. Their three fourth-quarter drives ended in punts and all went 30 yards or less as the offense continued to sputter late.
Crabtree's catch proved to be the game winner. He pierced New York's defense with a post route up the left side and outran the secondary to the goal line. He finished with three catches on eight targets for 85 yards.
Quarterback Colin Kaepernick completed 15 of 29 throws (52 percent) and added 24 on the ground. It was the second-straight week Kaepernick failed to complete 60 percent of his passes after doing so in six of his first eight games.
"Our defense played great. I think that was the biggest thing we got from this game. They continue to play great and put us in a position to win," Kaeperick said.
The Giants reached into their back pocket and surprised the 49ers with an onside kick in the third quarter after Josh Brown's 43-yard field goal cut the deficit to six. Bubba Ventrone had the ball in his arms, but had it ripped away before taking possession. The play was reviewed and New York was given the ball.
Three plays later, however, Manning threw his third interception of the day when Reid picked him off on third-and-9 looking deep down field for Beckham.
The 49ers will fly home and take on Washington next week.